This is one of the frustrations of being a writer and a reader and an earnest student of grammar:

You go to all that trouble of learning a picayune rule--and then the masses go charging through it, ignoring it in the way bullheaded but powerful masses do, and you realize you learned the darned rule for nothing.

I learned the stupid distinction between healthful and healthy--and, honest to goodness, the AHD made the distinction between the two at least in the '60s. The first time I heard a commercial in which 'healthy' was misused, I nearly blew my stack. But why? For nothing. Because the masses bloody didn't like the sound of 'healthful'--the masses just plain avoid using the word 'healthful.' They like 'healthy.'

And one day some future tsuwm--some tsuwm with three heads and six arms and instant access to every linguistic element that ever existed, including Neanderthal grunts found still reverberating in some strange channel in the earth's core--that future tsuwm will use 'healthful' as a useless word of the day--a relic.

But, honestly, I cannot make myself say:

"Oh, that's a healthy choice!"

It makes my blood curdle, and, yes, I'm antiquated.

But I do like splitting infinitives because that's an altogether different situation, in my way of thinking.